A solder composition is a mixture in a form of a paste obtained by kneading a solder powder and a flux composition (i.e. a composition including a rosin-based resin, an activator, a solvent and the like) (see, for instance, Patent Literature 1: Japanese Patent No. 5756067). The solder composition is required to exhibit restraining effect of a generation of voids and excellent printability, as well as solderability such as solder melting property and a property of easily being wet and spread (i.e. solder wet-spreadability).
On the other hand, recent diversification of functions of electronic devices requires a large-sized electronic component to be installed on an electronic board. Further, some of the large-sized electronic components (e.g. power transistors) have a wide area of electrode terminals. Since the solder composition is printed over a large print area in such an electronic component, large-diameter voids are likely to be generated.
It has been studied to use a highly viscous solvent with a high boiling point (e.g. isobornyl cyclohexanol) in a solder composition in order to reduce the large-diameter voids. However, it is found that the use of such a highly viscous solvent with a high boiling point is not effective for reducing the large-diameter voids when the solder composition is applied to electronic components such as a power transistor having an electrode terminal with a large area.